Current generator with core cooling

ABSTRACT

A current generator, particularly for vehicles, has a shaft, a liquid cooled generator, a liquid cooled internal combustion engine forming a drive motor for the generator, and a pump for supplying a liquid coolant. The generator, the internal combustion engine and the pump are arranged coaxially on the shaft. The pump for a liquid coolant is located on the shaft between the generator and the drive motor.

BACKGROUND OF THE INVENTION

The present invention relates to a current generator, in particular formotor vehicles, which is composed of a liquid cooled generator and aliquid cooled internal combustion engine formed as a drive motor as wellas a pump for the liquid coolant, which are arranged coaxially on ashaft.

Such a current generator is disclosed, for example, in the German patentdocument G 86 01 003. The water pump which is required for the coolingis arranged outside of the motor so that it is easily accessible formaintenance.

An air cooled current generator is disclosed in the U.S. Pat. No.4,827,147. Current generators of this type have the advantage that theblower wheel does not need any maintenance. However, there are somedisadvantages. In order to avoid two separate blower wheels, a single,double acting blower wheel is arranged between the motor and thegenerator. Fresh air is aspirated in two partial streams separatelythrough the motor and through the generator and then jointly expelled.Thereby, the action of two separate blowers is obtained with one blowerwheel.

Furthermore, the U.S. Pat. No. 4,486,668 describes a generator with avacuum pump which is arranged between a driving V-belt pulley and thegenerator. The pump is easily accessible due to the belt drive. Acoaxial arrangement of the motor and generator shaft is thereby avoided.The generator is not cooled with liquid. The pump does not operate forcooling.

The German document DE 35 34 507 A1 describes exclusively an internalcombustion engine with a cooling water pump which has a magnet rotor.The pump is also easily accessible.

The known current generators have the same disadvantage that thearmature shaft bearings or drive motor shaft bearings fail especially innarrow space conditions, which affects the operational safety.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide acurrent generator which avoids the disadvantages of the prior art.

In keeping with these objects and with others which will become apparenthereinafter, one feature of the present invention resides, brieflystated, in a current generator, particularly for motor vehicles, whichhas a liquid cooled generator and a liquid cooled internal combustionengine formed as a drive motor and also a pump for a liquid coolantarranged coaxially on a shaft, wherein the pump for the liquid coolantis located on the shaft between the generator and the drive motor.

It is provided that the coolant pump is arranged between the generatorand the drive motor. As a result of this step, the cooling acts on boththese units. The arrangement saves space and results in anadvantageously high temperature gradient with respect to the coolerportion of the shaft on which the coolant pump is arranged.

Accordingly, the heat generated at the armature of the current generatoris guided off via the generator shaft and the heat from the crankshaftof the drive motor is guided directly to the heat sink, the coolantpump. Thermal failure of the shaft bearings is accordingly prevented.The life of the units is lengthened accordingly. The cooling of thegenerator according to the invention makes it possible to dispense withair cooling of the current generator. This advantageously reduces thedimensions of the current generator.

Since the coolant pump is arranged on the shaft, V-belts for externalcoolant pumps can be omitted in the current generator according to theinvention. The risk of injury due to rotating parts arranged on thecurrent generator is decreased as a result.

It is further provided that the shaft includes a generator shaft, pumpshaft, and drive-motor shaft which are connected with one another so asto be aligned. The cooling device is accordingly easy to separate fromthe generator and drive motor. Maintenance is also simplified. In amodular-type construction, the current generator can be assembledpiecewise depending on its intended use and circumstantial factors sothat costs for stocking parts and delivery times are advantageouslyreduced. In spite of the modular assembly of the generator, the heatgenerated in the armature of the generator is guided off by the armatureshaft via thermal contact with the pump shaft over a large surface area.

Since the connection between the armature shaft and pump shaft isconstructed as a self-centering conical snug fit, the pump shaft isaligned with the armature shaft so as to be self-centering. Misalignmentand resulting high bearing wear are accordingly prevented.

In a development of the invention the coolant pump is constructed as amagnetic impeller pump. The current generator is accordinglyparticularly easy to service, since rotating sealing surfaces or sealsare entirely dispensed with. In addition, the space requirement isfurther reduced, since a magnetic impeller pump has small dimensions inthe axial direction.

The coolant is delivered in the simplest possible manner in that themagnetic impeller pump has a blade impeller constructed as a magneticimpeller and a stationary pump housing with coolant suction line andcoolant pressure line connected thereto. The coolant suction line andcoolant delivery line are preferably attached to the outer surface ofthe housing in the radial direction. Accordingly, the line connectiondoes not require any additional space in the axial direction. Further,the coolant line connections are easily accessible for maintenancepurposes.

By arranging a sliding bush between the pump housing and the shaft todirect heat from the shaft into the pump housing, the heat generated inthe generator and drive motor and released on the shaft is transmittedin a particularly efficient manner to the stationary pump housing byheat conduction. The transmission of heat to the pump housing isincreased by the relatively high temperature gradients between the shaftand coolant. A thermal lubricant is advantageously introduced betweenthe sliding bush and shaft for a further improvement in the heatconduction.

In another development of the invention the coolant pump is acentrifugal pump, in particular a self-priming centrifugal pump. Thistype of pump is especially robust and is also impervious to dry running.

In another construction of the invention the coolant pump has astationary pump housing with coolant suction line and coolant deliveryline and a blade impeller connected with the pump shaft so as to befixed with respect to rotation relative to it. The coolant suction lineis guided into the pump housing as far as the radial inner region of theblade impeller in a plane situated vertically relative to the pumpshaft. The coolant suction line is accordingly arranged in the pumphousing in a radial to tangential direction and leads up to the innerdiameter of the blade impeller. The coolant is accelerated outwardcentrifugally from there by the rotating blade impeller and is guidedout via the coolant delivery line in the outer area of the housing. Thecoolant pump can accordingly be arranged between the drive motor andgenerator so as to economize on space in an advantageous manner withoutthe shaft being lengthened so as to cause thermal disadvantages andtechnical problems related to the bearings in the case of suction lineswhich are conventionally guided axially in centrifugal pumps.

The pump can be produced cheaply in that the pump housing is composed ofa central pump part and two preferably identical pump covers. Inparticular, fewer replacement parts must be stocked in that the coolantsuction line and coolant delivery line are arranged in the central pumppart.

The central pump part is preferably made of high-quality steel and thepump covers are made of polyamide. This makes for a lower weight of thepump housing and also improves the thermal insulation, in which the heattransmitted from the pump shaft to the coolant is efficiently guided offfrom the generator area. The high-grade steel pump housing requirespractically no maintenance.

As a result of the aforementioned advantages the current generator hassmaller dimensions and a higher output coefficient.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a longitudinal section of a current generator with drivemotor and generator and with a centrifugal pump arranged between thelatter;

FIG. 2 shows a cross section of a central pump part of the centrifugalpump along line 2--2 in FIG. 1;

FIG. 3 shows a schematic longitudinal section of a current generatorwith drive motor and generator and with a magnetic impeller pumparranged between them.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows a current generator which has a drive motor B and agenerator A. A centrifugal pump 1 is arranged on a common shaft (4, 7,15) between the generator armature 8 of the generator A and thecentrifugal mass 9 of the drive motor B.

The shaft (4, 7, 15) is divided into three portions: a generator shaft7, a pump shaft 4, and a drive-motor shaft 15. The generator shaft 7 andthe pump shaft 4 are connected via a conical snug fit 6 which istensioned with a screw 13 arranged in the axial line of the armatureshaft 7. The shaft portions which are securely connected in this way arethereby aligned in an exact manner and thermally coupled with oneanother via the surface of the conical snug fit 6.

A blade impeller 2 is attached to the pump shaft 4 by atongue-and-groove connection 21 so as to be fixed with respect torotation relative to it. The blade impeller 2 is formed on at acylindrical sleeve 16 which extends roughly over the width of thecentrifugal pump 1 and has thermal contact with the pump shaft 4 over alarge surface area. Bearings 10 which rotatably support a stationarypump housing (5, 3, 5) on the pump shaft 4 are arranged on the outsideof the cylindrical sleeve 16.

The stationary pump housing (5, 3, 5) of the centrifugal pump 1 has acentral pump part 3 made of high-quality steel and two identical pumpcovers 5 made of polyamide which are arranged at the front of thecentral pump part 3. These three structural component parts are screwedtogether by screws 14 and, together with the blade impeller 2, form thecentrifugal pump 1.

The coolant is fed to the interior 17 of the centrifugal pump 1 via acoolant suction line 11 arranged radially in the central pump part 3.The coolant is accelerated by the rotational movement of the bladeimpeller 2 and guided into an outer annular sector 18 of the centrifugalpump 1 and from there is guided outward via a short coolant deliveryline 12 arranged radially in the central pump part 3.

The centrifugal pump 1 is sealed with sealing rings 20 between the pumpcovers 5 and the blade impeller 2 in two radial areas at the cylindricalsleeve 16 on one side and at an outer sealing surface 19 on the otherside.

FIG. 2 shows that the central pump part 3 is constructed so as to bedivided in the radial direction for mounting the centrifugal pump 1. Thetwo halves of the central pump part 3 can be connected via tangentiallyarranged screws.

FIG. 3 shows an embodiment example with a coolant pump which isconstructed as a magnetic impeller pump 22 and is likewise arrangedbetween the drive motor B and generator A. The magnetic impeller pump 22has a pump housing 24 and a blade impeller 23 which is arranged thereinso as to be rotatable. The blade impeller 23 is outfitted with apermanent magnet 26 which is integral with an annular surface. Locatedopposite this permanent magnet 26 are permanent magnets 27 on astructural component part, e.g. a centrifugal mass 9, driven by thedrive motor. The blade impeller 23 of the magnetic impeller pump 22 isaccordingly driven by the centrifugal mass 9 without contact. Themagnetic impeller pump 22 works as a centrifugal pump.

The coolant suction line 11 leads into the pump housing 24. The coolantdelivery line 12 is arranged opposite the latter.

A sliding bush 25 is arranged between the pump housing 24 and the pumpshaft 4 to improve the heat conduction. The sliding bush 25, e.g. acommercially available cast-bronze bearing bush, contacts the pump shaft4 on the inside so as to be rotatable and is securely connected at theoutside with the pump housing 24. A heat-conducting lubricant 30 ispreferably introduced in a suitable manner into the sliding surfacebetween the sliding bush 25 and the pump shaft 4. This improves the heatconduction between the rotating pump shaft 4 and the stationary slidingbush 25 and reduces friction.

A spacer disk 28 which is preferably made from ceramic material isarranged between the appropriate abutment at the rotatable centrifugalmass 9 and the stationary pump housing 24 so as to improve the startingcharacteristics of the magnetic impeller pump.

Cooling ribs 29 are formed on the side of the pump housing 24 facing thegenerator A for improved cooling action. The flow of air generated bythe rotating movement of the generator armature 8 is cooled at thecooling ribs 29. This further reduces the operating temperature of thegenerator A.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofconstructions differing from the types described above.

While the invention has been illustrated and described as embodied in acurrent generator with core cooling, it is not intended to be limited tothe details shown, since various modifications and structural changesmay be made without departing in any way from the spirit of the presentinvention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this invention.

LIST OF REFERENCE NUMBERS

A generator

B drive motor

1 coolant pump (centrifugal pump)

2 blade impeller

3 central pump part

4 pump shaft

5 pump covers

6 conical snug fit

7 generator shaft

8 generator armature

9 centrifugal mass

10 bearing

11 coolant suction line

12 coolant delivery line

13 screw

14 screw

15 drive-motor shaft

16 cylindrical sleeve

17 interior

18 outer annular sector

19 outer sealing surface

20 sealing ring

21 tongue-and-groove connection

22 magnetic impeller pump

23 blade impeller

24 pump housing

25 sliding bush

26 permanent magnet

27 permanent magnet

28 spacer disk

29 cooling ribs

30 lubricant

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims.
 1. A current generator, particularlyfor vehicles, comprising a shaft; a liquid cooled generator; a liquidcooled internal combustion engine forming a drive motor for saidgenerator; a pump for supplying a liquid coolant, said generator, saidinternal combustion engine and said pump being arranged coaxially onsaid shaft, said pump for a liquid coolant being located on said shaftbetween said generator and said drive motor, said pump for a liquidcoolant being formed as a magnetic impeller pump, said magnetic impellerpump having a blade impeller which is formed as a magnetic impeller, anda stationary pump housing with a coolant suction line and a coolantdelivery line; and a sliding bush for conducting heat from said shaftinto said pump housing, said sliding bush being arranged between saidpump housing and said shaft.
 2. A current generator as defined in claim1, wherein said shaft is subdivided into three shaft portions, includinga generator shaft portion, a pump shaft portion and a drive motor shaftportion, said shaft portions being connected with one another so as tobe aligned with each other.
 3. A current generator as defined in claim2; and further comprising means for connecting said generator shaftportion and said pump shaft portion and including a self-centeringconical snug fit.
 4. A current generator as defined in claim 2, whereinsaid pump for a liquid coolant is formed as a centrifugal pump.
 5. Acurrent generator as defined in claim 4, wherein said centrifugal pumpis a self-priming centrifugal pump.